Mount rack hardware to wood.

You need M6 rack mount screws with washers (to protect your gear) and fitting square nuts. I removed the retention springs from the nut, the slot in the print is captive. 

Also shop for SPX3.5mm spax wood screws in the right length for your wood part.

M6 Cage Nuts, Bolts and Washers Kit 

or German:

M6-Käfigmuttern und Schrauben für Rack Mount Equipment Server